Structure and Characteristics of Internal Wave Field in an Ocean Frontal Region East of Malta in Mediterranean

Abstract

The structure and characteristics of the internal wave field (coherence, frequency spectra, phase velocities, dispersion of velocity fluctuations) observed in an ocean frontal zone on the shelf-slope east of the island of Malta is studied. Using spectral and coherence analysis of temporal temperature variations measured by two thermistor chains 7 km apart the near-inertial internal gravity waves (NIWs) were detected, and their wavelengths and trace velocities were estimated. The temperature, salinity and density front that existed during the measurement period and the bottom irregularities of island’s shelf are both proposed to be the sources of the observed NIWs and internal waves of different periods. The mechanism of formation of the frequency spectrum of the observed internal wave field is proposed. By analyzing the effect of advection of internal waves by an alternating current induced by all the internal waves the observed periodic change of the sign of the trace velocity of the internal waves is explained.